Biodegradation of mulching films Sedki BEN ALI Supervisors: Richard Gattin, Nathalie LEBLANC Research Unity:Agri’terr-Esitpa International Conference and Exhibition on Biopolymers and Bioplastics August 10-12,2015 San Francisco, USA

The French Environment and Energy Management Agency (ADEME) Public agency under the joint authority of the Ministry of Ecology, Sustainable Development and Energy, and the Ministry for Higher Education and Research Provides expertise and advisory services to businesses, local authorities and communities, government bodies and the public at large, to enable them to establish and consolidate their environmental action. Helps finance projects, from research to implementation, in the areas of waste management, soil conservation, energy efficiency and renewable energy, air quality and noise abatement. Agricultural engineering college  500 students 1 research unit, AGRI’TERR, made up 17 researchers 7 PhD students in post-graduate

2 topics: – Interaction plant/soil/micro-organisms (focus on bacteria and fungi: abundance, biodiversity, functions) – Non-food valorization of agro-resources and by-products to elaborate agro-materials (relation structure, functions, properties of agro- materials) for different applications: – Packaging, – Building – Car industry – Agriculture (mulching films)

PLAN Introduction I-characterization and composition of materials before the biodegradation test II-Biodegradation test of mulching films -Evolution of materials during the test TGA, SEM, IR, NMR… -Biological Follow up of the biodegradation test Microbial Carbon, DNA extraction Conclusion

Control of soil humidity and temperature Reduction of water evaporation and irrigation frequency Optimisation of growth conditions by maintaining soil microenvironment Reduction of weeds and plant deseases: reducing the use of herbicides, pesticdes… + Formed by synthetic plastic PE The deposit of Farm films estimated by ADEME at about tones/year - Environmental pressure Mulching films? introduction

Waste Management Application of the 2002 Waste Act Prohibition to bury, burn or to landfill these bulky and dirty films Legislative pressure Landfill 59% Waste to Energy 27% Recycling 7% Incineration 7% ² introduction

Biodegradable mulching films, solution? Oxo-biodegradable 98% of PE Adding an oxidizing agent (accelerate the fragmentation process by heat/photodegradation) Mulching films « Biodegradable » Starch cellulose Aliphatic aromatic polyester Biodegradable mulching films Ecological cycle BIONOV®, Biotec… introduction

T d = 295°C Starch T d = 395°C PBAT 295°C 395°C Films characterization before the test TGA IR NMR 18,63% 75% BIONOV®

Films characterization before the test TGA IR NMR 14,95% 74,98% T d = 295°C Starch T d = 395°C PBAT Biotec

ester function Aromatic group hydroxyl function Alkyl group 3400 cm cm cm cm cm cm -1 Films characterization before the test TGA IR NMR Based on the structure of PBAT several functional groups, such as hydroxyl (OH) and carbonyl (CO) groups can be used as tools to study degradation

C6H4C6H4 Films characterization before the test TGA IR NMR OCOCH 2 NMR spectrum of PBAT with aromatic peak at 8.06 ppm, and OCOCH 2 (adipate fraction) at 2.29 ppm

Biodegradation test NaOH solution Activated inert solid medium Pouzzolan Mulching film Biodegradation of mulching films under simulated soil conditions/ ISO17566 Inert solid medium « pouzzolan » -No additional CO2 production -Easy chemical extraction -Water holding capacity Mineral solution Soil microbial extraction

Films characterization during the test SEM TGA IR Mineralization Biotec BIONOV® 0 day 77 days180 days 77 days

Films characterization during the test BIONOV® The samples presented less stages of thermal degradation as long as the test progress. The thermal degradation stage related to starch disappear along the test. T0 T1 T2 T3 T11 SEM TGA IR Mineralization

BIONOV® 18.63% 15% 9.88% 8.12% 7.9% 5.67% 5.35% 5.24% 5.23% 4.37% 4.13% Films characterization during the test The first peak decreased gradually with the exposure time (with a relative increase of the second peak) This result is an indication that starch is the most bio-susceptible material of the matrix SEM TGA IR Mineralization

Films characterization during the test Less stages of thermal degradation as long as the test progress. The thermal degradation stage related to starch disappear along the test SEM TGA IR Mineralization T0…T11 Biotec

12.77% 14.95% 2.21% 3.5% 3.72% 3.94% 4.70% 4.72% 4.73% 4.88% 4.94% 7.95% Films characterization during the test SEM TGA IR Mineralization Biotec

0 month 6 months Reduction of the carbonyl absorbance Increase of the hydroxyl absorbance Films characterization during the test Terminal alcohol and carboxylic acid groups are produced due to main chain scission from hydrolysis of ester linkages SEM TGA IR Mineralization BIONOV®

Soil total microbial biomass was determined using the chloroform fumigation extraction method Biological Follow up of the biodegradation test Microbial Carbon DNA extraction Similar evolution Increase untill 63 days Progressive decrease until the end of the test

Similar DNA evolution for both films Slower biodegradation for Biotec film is expected. Biological Follow up of the biodegradation test Microbial Carbon DNA extraction *DNA was extracted from 500mg of pouzzolan using FastDNA SPIN Kit for soil and was quantified by fluorimetric measurement of the Hoescht fluorochome

TGA SEM Mineralization Films characterization during the test Higher mineralization for Bionov comparing to Biotec More starch in the composition of Bionov than in Biotec

Conclusion  The biodegradation of the films is pimarily due to a selective consumption of starch (facilitate the penetration of water inside of the matrix) hydrolysis of ester goups  Terminal alcohol and carboxylic acid groups are produced due to main chain scission from hydrolysis of ester linkages.  The ester groups of amorphous regions of PBAT is more susceptible to hydrolysis than ester roups in crystalline regions.  Mineralization very active at the begining of the test. In this study we also showed:  No toxic effect was observed of monomers (PBAT) on plants and earthworms.  Identification of responsible microorganisms (fungi) of biodegradation is in progress.

Tkhanks for your attention…